Energy recovery system for absorption heat pumps

ABSTRACT

An improvement in an absorption refrigeration and/or heating system including apparatus (157) to convert the pressure energy and/or phase change energy in the solution and/or refrigerant of the absorption system into mechanical energy, with additional apparatus to replace or supplement the externally supplied mechanical energy motive device (152) in the system with the converted mechanical energy. The system includes a first positive displacement pump (98) for conveying the absorbent solution from the absorber to the generator with first positive displacement apparatus (98) driven by a motive device (152) that is activated by the externally supplied energy. A second pump (158) is provided that is driven by the system pressure energy. Each of the pumping apparatus is being independently driven and connected to the other only by fluid connection.

FIELD OF THE INVENTION

This invention relates to a cooling and heating system which operates onthe absorption and phase change heat exchange principle. Moreparticularly it relates to a continuous heat actuated, air cooled,multiple effect generator cycle, absorption system.

In further aspects, this invention relates to improvements to the systemconstructed for use with an absorption refrigeration solution paircomprising a nonvolatile absorbent and a highly volatile refrigerantwhich is highly soluble in the absorbent. A disclosed refrigerant pairis ammonia as the refrigerant and sodium thiocyanate as the absorbent.

BACKGROUND OF THE INVENTION

The background of this invention is found in U.S. Pat. No. 4,646,541(hereinafter the Prior Patent) which discloses the general subjectmatter of this invention. This invention therefore should be consideredwith reference to this Prior Patent which includes the common inventorsF. Bert Cook and Edward A. Reid, Jr. and is assigned to the sameassignee as this invention.

U.S. Pat. Nos. 4,742,693, 4,719,767, 4,691,532, 4,742,687, and 4,722,193are sibling patents of the Prior Patent and are pertinent to thedisclosure of this invention providing further background information onthis subject matter.

In the quest for improvement in Absorption Refrigeration and Heat PumpSystems, the common measure of performance is the often referred to"coefficient of performance", i.e., COP. As used herein, coefficient ofperformance, i.e, COP, is defined as the energy transferred at the loadin a unit of time divided by the energy provided to the system in thesame unit of time which is well understood by those skilled in the art.Other measures of performance include reduction in complexity; or statedconversely, apparatus and system simplification.

Absorption systems are usually very efficient during the heating cycle,when a source of heat, such as a natural gas flame is used. On the otherhand, these systems are less efficient in the cooling cycle.

Air cooled refrigeration circuits of the mechanical vapor compressiontype have also been demonstrated which can be reversed to provide eitherheating or cooling to a load by switching the flow of an intermediateheat transfer solution typically consisting of water and antifreezesolutions such as ethylene glycol, etc.

Liquid cooled absorption refrigeration circuits using the double effectgenerator cycle to achieve high efficiency are commercially available.However, these systems using water as the refrigerant are not suitablefor use in heating a conditioned space (the heating load) since therefrigerant freezes at 32° F. and therefore cannot be used in a spaceheating system at ambient outside temperatures below approximately 40°F.

Absorption refrigeration and heat pump systems are well known in theirbasic operating characteristics and need little further descriptionexcept to establish the definitions and context in which this inventionwill be later described.

In a typical system a refrigerant, water or other phase change materialis dissolved in an absorbent (typically lithium bromide or other salts)and these are often called the "solution pair". The refrigerant isabsorbed or desorbed (expelled) in or out of solution with the absorbentto varying degrees throughout the system and the heat of absorption isadded or extracted to produce heating and cooling effects.

The solution pair enters a generator where it is subjected to heat andthe applied heat desorbs (expels) a portion of the refrigerant in theform of a vapor which is conveyed to the condenser. There, externalcooling condenses the refrigerant vapor to liquid, which is conveyedthrough an expansion valve, into an evaporator where heat is gained. Inthe refrigeration system operation the heat gained in the evaporator isfrom the cooling load.

The low pressure vapor then passes to an absorber where cooling allowsthe absorbent solution to absorb the refrigerant vapor. The solution isthen conveyed to a recuperator by a pump. The recuperator is acounterflow heat exchanger where heat from the absorbent/refrigerantsolution flowing from the generator to the absorber, heats the returningsolution pair flowing from the absorber to the generator. In the heatingcycle, the cooling applied at the absorber and/or the condenser is theheat delivered to the heating load.

As a matter of convenience and terminology herein, each part of theabsorption system which operates at the same pressure is termed achamber.

Conventional absorption refrigeration/heating systems are two chambersystems although three chamber systems appear in the prior art and haveseen limited use. When operated as heat pumps, two chamber systems giverespectable heating performance but give poor cooling performance.

Using ammonia (NH₃) as the refrigerant and water (H₂ O) as the sorbent,heat pumping can occur from an ambient air source which is attemperatures below freezing. Where the air is treated as if it were dryso that no defrosting is necessary, the typical two chamber NH₃ /H₂ Oheat pump would represent a significant improvement over what would beexpected of a simple furnace. However, since heat pumps are moreexpensive than furnaces, cooling season performance benefits are neededto justify the added expense. In other words, the heat pump must act asan air conditioner also to offset the additional cost of the heat pumpcombined with separate installation of an air conditioner with afurnace.

For cooling, an NH₃ /H₂ O system is predicted to have a COP equal toabout 0.5. This low performance index causes unreasonable fuel (orenergy) costs from excessive fuel (or energy) use.

Three-chamber systems of various types have been suggested which wouldimprove the performance by staging the desorption process into effects.This allows for increasing the actual temperature at which the drivingheat is added to the system (cycle). Until the invention of U.S. Pat.No. 4,646,541 it was thought that this increase in temperature wouldrepresent an unreasonably high pressure, especially from ammonia/watersystems, and would force the system to operate in regions for which datais not readily available.

In addition the pressure has tended to rule out ammonia/water in athree-chamber system. The search for organic materials such ashalogenated hydrocarbons and other refrigerants as a replacement for theammonia has been limited by fluid stability at these highertemperatures. Normal organic refrigerant stability tests have indicatedthat it is necessary for oil to be present for operation in vaporcompression refrigeration systems. These high operating temperaturesrule out most of the common refrigerants, particularly from being heateddirectly by combustion products which often cause local hot spots, whichresult in working fluid degradation and/or corrosion of components.

The heat actuated, air cooled, double effect generator cycle absorptionrefrigeration system of Prior Patent (U.S. Pat. No. 4,646,541) and thesibling patents therefrom overcome limitations of the existing prior arttechnology. The air cooled system therein eliminated the need forcooling water and the use of ammonia as the refrigerant avoidsrefrigerant freezing during heating operation. The double effectgenerator cycle permits high efficiency through internal heat recoveryin the absorption refrigeration circuit. The use of sodium thiocyanateas the absorbent eliminates the need for analyzers and rectifiers topurify the refrigerant stream with the resultant loss of unrecoverableheat.

This invention is directed to further improvements and simplificationsof the above described prior patented system. It applies to anintegrated three-chamber system having one solution pair using amaterial of unusual fluid stability at higher temperatures whenmanipulated in an apparatus and system to take advantage of itsproperties. The typical preferred solution pair for operation as part ofthe system and components of this invention is ammonia as therefrigerant and sodium thiocyanate as the absorbent.

SUMMARY OF THE DISCLOSURE

In summary, this invention is an improvement to the energy recoverysystem of the Prior Patent and provides that in a system having at leastone generator, a condenser, an evaporator, and an absorber, whereinrefrigerant is absorbed and desorbed in an absorbent solution, and theapplication of heat and externally supplied mechanical energy iscombined and converted to pressure energy that is applied to, orremoved, from a solution of refrigerant and absorbent, there shall bethe following: (a) means to convert the pressure energy and/or phasechange energy in the solution and/or refrigerant to mechanical energy;(b) means to replace or supplement the externally supplied mechanicalenergy; and (c) with the said system including a first pump means, thatis driven by the externally supplied mechanical energy, for conveyingthe absorbent solution from the absorber to the at least one generatormeans, and a second pump means, independently driven by the pressureenergy of the system, additively connected to the first pump means, tocombine the output of the first and second pump means at the maximumsystem pressure.

The foregoing and other advantages of the invention will become apparentfrom the following disclosure in which a preferred embodiment of theinvention is described in detail and illustrated in the accompanyingdrawings. It is contemplated that variations and structural features andarrangement of parts may appear to the person skilled in the art,without departing from the scope or sacrificing any of the advantages ofthe invention which are delineated in the included claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of the double effect absorption system of thisinvention in the cooling mode.

FIG. 2 is a diagram of the hydronic working fluid subsystem of thedouble effect absorption system of this invention in the heating mode.

FIG. 3 is a diagram as in FIG. 2 of the double effect absorption systemof this invention in the defrost mode.

FIG. 4 is a cross-sectional elevational view of the evaporator apparatusof this invention taken on the line 4--4 of FIG. 6.

FIG. 5 is a schematic elevational sectional view of one embodiment ofthe apparatus and system of this invention as it could be constructedfor installation adjacent to a building having a cooling and/or heatingload.

FIG. 6 is a schematic plan view of the embodiment of the apparatus shownin FIG. 5.

FIG. 7 is a cross-sectional elevational view of thegenerator/recuperator module of this invention taken on the verticallongitudinal axis 7--7 of FIG. 5.

FIG. 8 is a elevational perspective view of the separator components ofthis invention.

FIG. 9 is a schematic cross-section elevational view of theabsorber/condenser module of this invention with auxiliary components.

FIG. 10 is a schematic diagram of one embodiment of the energy recoveryapparatus arrangement of this invention.

FIG. 11 is a schematic diagram of one embodiment of the energy recoveryapparatus arrangement of this invention.

FIG. 12 is a schematic view of an alternative energy recovery unitincluded in this invention.

FIG. 13 is a schematic view of an alternative addition to the system ofthis invention for the purpose of providing domestic hot water.

DETAILED DESCRIPTION OF A BEST MODE OF PREFERRED PRACTICE OF THEINVENTION

In the description of this invention, it is important that there is aclear understanding of the meanings of the terms used herein. Otherwise,because of the complexity of the entire system and the use of componentsfrom various fields of mechanical, chemical, and electrical arts, theterminology could be confusing in some cases.

Therefore, as used herein the term "strong solution", when speaking ofthe solution pair refers to that solution that has picked up refrigerantin the absorber and is in progress toward the generator and carries ahigher ratio of refrigerant to absorbent than solution which has beendesorbed and partially expelled cf refrigerant in the generator(s) ofthe system. Solution from which refrigerant has been expelled is, bycontrast, a "weak" or weaker solution holding a lesser ratio ofrefrigerant to absorbent in solution.

In the three chamber system of this invention, a solution of"intermediate" strength is employed between the generator means. Thissolution is by definition, weaker than strong solution and stronger thanweak solution.

The terms "generator" and "desorber" are synonymous. The term "heatexchanger" defines apparatus where fluids are passed in close proximityto each other separated only by a usually impervious wall through whichthe heat from the warmer is conducted to the cooler. Conventionally, itis understood that heat passes from the hot fluid to the cold fluid.

As used herein, the term "heat exchanger" defines an apparatus whichexchanges heat into or out of the system; i.e., with an external fluidsuch as ambient outdoor air, or ground water, or working fluid. Thoseapparatus which exchange heat within the system are termed"recuperators".

As further used herein, the term "working fluid" defines the fluid usedto transfer heat to or from the load or heat sink. Preferably this is anethylene glycol and water solution which is capable of remaining anunfrozen liquid at temperatures colder than liquid water alone. However,other working fluids such as calcium chloride and water could also beused.

As described in the Background Of The Invention portion of thisdisclosure, a double effect generator absorption system in which thethermo/physical properties are enhanced by the application of a sodiumthiocyanate/ammonia absorbent/refrigeration pair, with generator andheat exchanger in a stacked coil configuration including tube-in-tubeconcepts, together with the combination of energy recovery motors tocontribute to the power requirement of the solution pump required andfound in absorption refrigeration systems, form the basis for theimprovements to be further described below. Although sodiumthiocyanate/ammonia are the preferred absorbent/refrigerant pair, otherabsorbents and refrigerants can be used including methyl or ethyl amineas the refrigerant and alkali metal nitrates or thiocyanates as theabsorbent.

While the invention therein is a quantum leap forward in the applicationof methods and the construction of apparatus of heat driven absorptionrefrigeration and heat pump systems, and in particularly through theselection of the solution pair "ammonia as the refrigerant and sodiumthiocyanate as the sorbent", it has been found that various improvementswill be made with the methods and apparatus of this invention.

Double Effect Generator Absorption System with Switching BetweenCooling, Heating, and Defrosting

An absorption heat pump conceived to provide both space heating andspace cooling must be able to be reversed between the heating and thecooling modes without adversely effecting the operation of theabsorption refrigeration cycle. It is conceived in this invention thatthe double effect absorption heat pump shall remain operating in thesame manner and in the same apparatus components for both the heatingand cooling modes of operation. This method and apparatus of operationis uniquely conceived in connection with the application of surprisinglyeffective heat transfer components and methods provided in an improvedgenerator/recuperator apparatus and in an improved condenser/absorbercombination to be further described in detail as follows. Thearrangement of working fluid switching valves and control components arecontributing features in the invention.

Referring to FIG. 1 a first generator means 80 feeds a heated strongsolution 83 to a first separator 91. In the first generator means 80 andthe separator 91, a vapor refrigerant 82 is desorbed and separated bythe application of heat from a source 84, such as a gas flame.

A preferred construction of the first generator means 80 is shown inFIG. 7.

A solution of intermediate strength 85 remains in separator 91 and isconveyed to a first recuperator means 86 and then through a throttlingvalve or energy recovery motor 87 to a second generator means 81. Heatfrom the refrigerant vapor 82 is exchanged with the intermediatesolution 85 in the second generator 81. Additional vapor 82 is desorbedfrom the intermediate solution 85 leaving a weak solution 89 in a secondseparator 92.

The weak solution 89 passes through a second recuperator 95 and athrottling valve 96 with a connection at 93, and into an absorber means97. The weak solution 89 absorbs vaporous refrigerant 82 becoming astrong solution 83 which is pumped by a solution pump 98 successivelythrough recuperators 95 and 86 back to the first generator means 80.

Liquid refrigerant 82 is conveyed from the separator 91 through anexpansion valve or energy recovery motor 105, and through a condenser100 by way of a connection 94. Additional refrigerant vapor 82 fromseparator 91 is conveyed to the condenser 100 through the connection 94.

From the condenser 100 liquid refrigerant 82 is conveyed through a thirdrecuperator 107, to an evaporator 115, by way of an expansion valve 110.

Cool low pressure refrigerant is returned from the evaporator 115through the recuperator 107, exchanging heat with the warm liquidrefrigerant 82, and passing to an accumulator 205.

In the accumulator 205, excess refrigerant 82 is collected which mayhave occurred as a result of changes in the amount of refrigerantcontained in the condenser 100 and evaporator 115 because of theiroperation at different conditions, especially differences betweencooling, heating, and defrost modes of operation. By this arrangement,the system refrigerant concentration may ideally be controlled betweenabout 46% and about 32%.

From the accumulator 205 refrigerant joins the weak solution 89 at theconnection 93. From the connection 93 the combined weak solution andrefrigerant pass through the absorber 97 to a purge pot 99 thence to theinlet of a solution pump 98. By this process weak solution 89 absorbsvaporous refrigerant 82 becoming a strong solution 83 in the absorber97, and is pumped by a solution pump 98 back to the first generatormeans 80, passing successively through recuperators 95 and 86.

This improvement invention includes a separate hydronic subsystemthrough which a working fluid is conveyed among the various componentsof the double effect absorption refrigeration system, and between theload and heat source or sink.

Referring again to FIG. 1, the subsystem is depicted as a single fineline, which is connected to the inlet of the condenser 100 and passesthrough to a first four-way fluid valve 101 which is set to continue theflow to the inlet 103 of the absorber 97. After passing through theabsorber 97, the fluid is conveyed from an outlet 104 to a secondfour-way valve 106, and fed to an inlet of a first outdoor heatexchanger 108. From the first heat exchanger 108 the working fluid isconveyed through a pump 109 to a third four-way valve 112 which has beenpositioned to return the working fluid to an inlet 113 of the condenser100. By means of these connections, the heat of condensation andabsorption of the hot refrigerant 82 is exchanged to the working fluidin the condenser 100 and absorber 97 which transfer the heat through theworking fluid to the ambient outside air by heat exchange in the firstheat exchanger 108. A fan 114 induces air flow across the first heatexchanger 108 increasing the rate of heat exchange to the outsideambient air.

In this cooling mode operation, the outlet 104 of the absorber 97 isconnected from a joinder 116 through the first four-way valve 101 to theinlet 118 of the evaporator 115 at a joinder 117. No flow takes placebetween the joinders 116 and 117 in this mode, because there is nodifferential pressure in the working fluid between these two points andthere is no return path. Therefore, flow cannot occur.

In this mode of operation, the working fluid is conveyed from an inlet118 through the evaporator 115 to an outlet 119. From the outlet 119 ofthe evaporator 115, the working fluid is conveyed to four-way valve 106and thence to the indoor second heat exchanger 121, via valve 106 whereair from the conditioned space passes in heat exchange relationship withthe working fluid. A fan 122 induces air flow across the coils of heatexchanger 121.

From the indoor heat exchanger 121, the working fluid is conveyed by apump 123 past the joinder 117 and through the third valve 112 to theinlet 118 of the evaporator 115.

In this mode of operation the working fluid is cooled as it passes inheat exchange relationship with the cooled refrigerant in the evaporator115. The cooled working fluid transfers this cooling to the indoorconditioned air in the second indoor heat exchanger 121.

Referring to FIG. 2, the double effect generator absorption system andoperation remains the same for the heat pumping mode. However in thisheating mode, the working fluid subsystem is switched by means ofchanges in the position of four-way valves 106 and 112. The four-wayvalve 101 remains in the previous position as shown for the cooling modeof FIG. 1.

In this arrangement the hot working fluid from the condenser 100 isconveyed through outlet 102 and four-way valve 101 to the inlet 103 ofthe absorber 97. The subsystem provides cooling to the absorber becausethe combined refrigerant and weak solution are at higher temperature, sothat the necessary absorption process takes place in the absorptionrefrigeration system. The working fluid is heated further thereby andleaves the absorber 97 by way of outlet 104 to the four-way valve 106which is reversed from the previous cooling mode of operation. Theworking fluid now passes to the second heat exchanger 121 where itexchanges heat with the conditioned air of the living space (the load).Being cooled from the air in the living space, pump 123 directs theworking fluid back through valve 112 to the inlet 113 of the condenser100.

In this normal heating mode position of the four-way valves 106 and 112,the working fluid is conveyed from the evaporator 115 through theoutdoor heat exchanger 108 where it receives heat from the outdoor airbefore returning to the evaporator inlet 118. The fan 114 may beoperated intermittently depending on the outdoor air temperature andhumidity conditions to reduce frost build up on the heat exchangesurfaces. When the subsystem valves 106 and 112 are operating in thisposition, heat pumping occurs from the outside air to the evaporatorraising the temperature of operation of the subsystem providing for atheoretical COP of higher than 1.0.

It will be seen that in comparison to the system described in the PriorPatent, simplification and important reductions in first costs andoperating reliability have been achieved.

When the system is operating in the heating mode the first outdoor heatexchanger 108 is in communication with the evaporator and is absorbingheat from the surrounding outside ambient air environment. Under certainconditions of outside temperature and humidity the exterior surface ofheat exchanger 108 will accumulate frost from the moisture in thesurrounding atmosphere. An accumulation of frost on the surfaces of theoutdoor heat exchanger 108 reduces its heat exchange efficiencyhindering heat pumping operation and reducing the overall systemperformance. Various solutions have been proposed and are used in priorpractices to overcome this problem, such prior systems are inconvenientand draw down the COP of the unit by the requirement of additional heatenergy, such as by electrical resistance or the requirement for anauxiliary boiler.

However, in the operation of the system of this invention, defrosting isaccomplished when four-way valves 112 and 101 are reversed and four-wayvalve 106 remains as positioned for the heating mode. Air flow acrossthe second heat exchanger 108 is interrupted by shutting off the fan114. The warm working fluid from the condenser is directed through theheat exchanger 108 melting the frost. Heat from the absorber continuesto be directed through the second indoor heat exchanger 121 providingheat to the conditioned space although temporarily at a reduced rate fora short time. It is a feature of this invention that heat continues toflow to the load from the absorber 97 during the defrost cycle. In theconventional arrangements that have been provided to answer the frostingproblem of air transfer heat pumps, it is a practice to cut off the heatpump completely and use electrical resistance heaters to provide heatingduring defrosting. This invention to the contrary, maintains heat flowfrom the heat pump during defrosting and in most circumstances,defrosting can be completed before heat is required in excess of thatavailable during defrost operation. At the end of the defrost cycle, allthe working fluid reversing valves are returned to their normal heatingmode position, and the air flow over the first heat exchanger 108 isrestored.

Conventional controls are provided to sense the loss of efficiencyresulting from frost build-up and the defrost cycle is operatedautomatically.

As an alternative, the working fluid from the absorber 97 may be passedthrough a heat exchanger relationship with a storage tank for domestichot water when all the heat of the absorber means is not needed at theload, for instance when the outside ambient air is not cold or thesystem is operating in the cooling mode.

As shown in FIG. 13, a domestic hot water heater and tank 370 is locatedwithin the residence to which the heat pump system of this invention isinstalled. The outlet 104 of the absorber 97 is connected to an inlet371 of a heat exchange coil 372 in the hot water heater 370. An outletof coil 372 is connected to the inlet of the absorber 97. A secondsource of heat 375 such as a gas burner is also provided to the hotwater tank 370.

This domestic hot water heating subsystem is included in combination totake advantage of the excess heat available at the absorber undercircumstances where the full heating capacity of the system is notrequired for the ambient conditions being serviced by the load. Suchexcess heat may be available in either the cooling or heating modes whenthe system is not loaded to its designed capacity. In thosecircumstances when the system is not operating or there is no excessheat available at the absorber 97, the auxiliary burner may be operatedto assure that there is the required domestic hot water available.

A Living Space Environmental Conditioning Apparatus

A configuration for a living space, residential air conditioning andheating embodiment of this invention is shown in FIGS. 5 and 6, in whichan air conditioning and heating unit 165 is located outside a residenceand constructed in rectangular format on a base 167, and includes ahousing 166. The housing 166 includes an upper aperture 169. Theaperture is positioned above an ambient air inductive means such as thefan 114 (See FIG. 1). The first heat exchanger 108 comprises three sidesof the unit 165. Conveniently positioned as shown on the fourth side,are the solution pump 98, purge pot 99, evaporator 115, condenser 100,absorber 97, and recuperator 105. The separators 91 and 92 (as shown inFIG. 8 in longitudinally vertical position) are positioned nearby. Pumps123 and 109 for conveying the working fluid are juxtaposed to thesolution pumps 98 and 157. The second heat exchanger 121 and the fan 122are located within the living space.

Double Effect Generator and Recuperator Apparatus

Referring to FIGS. 5, 6, and 7, an embodiment of a double effectgenerator/recuperator means 220 is shown as apparatus which integratesin one interrelated assembly the various components and modules that areassociated with the use of the heat generated in a heat source 84. Tofacilitate understanding, numerical designations are the same as andrefer to like components in the system shown in FIG. 1.

Generator Module

As shown in FIG. 7, a generator unit or module 220 is generallysymmetrically constructed about a substantial vertical central axis.Generator module 220 includes a generator housing 221 that may becircular in the plan view (FIG. 6) and which is constructed on agenerator frame base 222 that may be the same or distinct from the base167 of the heating and air conditioning unit 165. Generator unit 220contains a circular floor 230 attached to the generator housing 221above the generator base 222 so as to contain insulating material 231.Generator floor 230 slopes gently from the center to the generatorhousing 221 so as to allow for the drainage of condensed moisture fromthe unit.

The generator housing 221 includes an upper generator shroud 223 and agenerator ceiling 224 between which is placed insulating material 225. Acylindrical passage 226 is formed by a cylinder 227 joining the centerportion of the shroud 223 and the center portion of the generatorceiling 224. A cylinder cap 228 seals the cylinder 227 from thesurrounding atmosphere and provides a mounting surface to whichgenerator blower 229 is attached. Cylinder cap 228 contains an aperture(not shown) that allows air from the blower 229 to enter the generatorunit 220 through cylindrical passage 226.

A central driving heat source 84 providing external heat to the system,typically a gas burner, is centrally positioned substantially on acentral axis 232 of unit 220. A gas source is not shown but it is to beunderstood to be of conventional piping design. Annular componentssurround the circular heat source 84 and include a first generator means(desorber means) 80, a first (high-temperature) recuperator means 86, asecond generator means 81, and a second (low-temperature) recuperatormeans 95. Each component is constructed as a plurality of coils,juxtaposed one to the next, in a substantially or generally annularcomposite form i.e., vertically positioned toruses or helices.Components are juxtaposed one to the next, and radially more or lessdistant from the central axis 232, i.e., surrounding the source of heat84 at varying distances. The generator 80 coils have fine fins thatallow for the passage of hot gases between and among the coils so as toachieve maximum heat transfer. See, for example FIG. 5 item 200 of U.S.Pat. No. 4,742,693 which is herein incorporated by reference. First andsecond recuperators and the second generator have coils with a solidexterior surface that are wound in contact with each other.

The recuperators, 86 and 95, and second generator 81, have an inner tubeand an outer tube arranged in what is often referred to as tube-in-tubeconstruction. Preferably the inner tubes have helical flutes 233 tobetter effect heat transfer between the fluids in the inner and outertubes. Fluted tubes are available commercially from suppliers such asTurbotec Products, Inc., Windsor, CT, and Delta-T Limited, Tulsa, OK.The liquid-liquid heat exchangers and absorbers have three flutes.Evaporators and condensers have four flutes and about three times asmany flutes per foot. That is, not only do the evaporators andcondensers have more flutes but they also are twisted more revolutionsper foot.

Tubing materials are conventional, being chosen for good heat transferthrough the walls of the tubing and corrosion resistance. Metals such asstainless steel and low alloy steels such as AISI 9260 and AISI 1075 aresuitable. Generator 80 is typically of conventional single tubeconstruction with small, fine fins.

In the preferred embodiment shown in FIG. 7, high-temperature air andcombustion products (flue gas) 245 are generated in a first generatorchamber and impinge upon the walls 131 of the tubular generator 80 beingdriven more or less downward and radially outward direction through thefins between the coils of generator 80 by blower 229. The hot combustionproducts 245 emerge through apertures 235 in cylindrical baffle 234 andflow downward along the solid inner cylindrical first recuperatorhousing 236 where they emerge through apertures 238 in the bottom ofinner recuperator housing 236.

The hot air and combustion products 245 then enter a second(recuperator) chamber 237 surrounding the first generator chamberthrough apertures 238 in the bottom housing 250 of the first recuperatorchamber 237. The hot air and combustion products 245 impinge upon thecoils of tube 249 of the first recuperator 86 while flowing in agenerally upward direction. The warm combustion products and air 245emerge into a third or outer chamber 240 of the generator unit from thesecond chamber 237 through apertures 312 located in the top portion ofthe outer recuperator housing 239. The warm combustion products and air245 impinge upon the coils of tube 252 of the second generator 81 andthe coils of tube 260 of the second recuperator 95 while flowing in agenerally downward direction. Combustion products and air 245 emergefrom the generator unit 220 through apertures 241 in the generatorhousing 221 located just above the generator floor 230.

The generator, recuperator, and other chambers are concentriccylindrical chambers juxtaposed one to the next. The general flow ofcombustion products and air is indicated by arrows in FIG. 7 as beinggenerally in a serpentine fashion, i.e. downward in the first chamber,upward in the second chamber, and downward in the third chamber.

The first generator means 80 is made from a finned double-wound helicalcoil of tubing. Strong solution 83 enters the first generator 80 fromthe first (high temperature) recuperator 86 through inlet 137 at atemperature of about 385° F. and a pressure of 1480 psia. The strongsolution 83 is heated by the heat source 84 as it flows downward throughthe outer winding of helical coil and then upward through the innerwinding of the helical coil emerging from the first generator means 80through outlet 138 at a temperature of about 415° F. The strong solution83 receives direct heat from the heat source 84 at a rate of about36,000 btu/hr.

As shown in FIGS. 1 and 8, the heated strong solution 83 then enters thefirst (primary) separator 91 through separator inlet 242 where itseparates into intermediate solution 85 and refrigerant vapor 82. Theintermediate solution 85 leaves separator 91 through lower outlet 243.The refrigerant vapor 82 leaves separator 91 through upper outlet 244.

Returning to FIG. 7, the intermediate solution 85 enters the firstrecuperator 86 through inner fluted-tube inlet 246. First recuperator 86consists of three rows of a fluted tube-in-tube helical windings locatedradially outwardly adjacent to first generator 80 and extendingvertically for almost the length of the first generator 80. The firstrecuperator 86 is contained in the cylindrical first recuperator chamber237 that is formed by inner cylindrical baffle 236, outer cylindricalrecuperator housing 239, the generator unit ceiling 224 and firstrecuperator housing bottom 250. As the intermediate solution 85 passesthrough the fluted inner tube 248 of recuperator 86, it exchanges heatto the strong solution 83 in the outer tube 249 of the recuperator 86 ata rate of about 69,000 btu/hr and leaves through the inner tube outlet247 at a temperature of 245° F. and a pressure of 1450 psia.Intermediate solution 85 is then throttled substantially isenthalpicallythrough valve 87 (FIG. and arrives at the secondary generator 81 at atemperature of 245° F. and a pressure of 290 psia.

The intermediate solution 85 enters the second generator means 81through outer tube inlet 251. The second generator 81 consists of tworows of fluted tube-in-tube helical windings located radially outwardlyadjacent to firs recuperator 86 and extending vertically along the topportion of the first recuperator 86. The second generator 81 iscontained in the upper portion of the cylindrical outer-mostgenerator-unit chamber 240 that is formed by the outer first recuperatorhousing 239, the generator unit housing 221, the generator unit ceiling224 and the generator unit floor 230. As the intermediate solution 85passes through the outer tube 252, approximately 18,000 btu/hr istransferred to it from the condensing refrigerant vapor 82 in the innerfluted tube 253. About an additional 1,000 btu/hr is transferred to theintermediate solution 85 in the outer tube 252 from the circulating fluegases 245. The intermediate solution 85 leaves the second generator 81through second generator outer tube outlet 254 at a temperature of 255°F. and a pressure of 290 psia.

As shown in FIGS. 1 and 8, the heated intermediate solution 85 thenenters the second (secondary) separator 92 through separator inlet 255where it separates into weak solution 89 and refrigerant vapor 82. Theweak solution 89 leaves separator 92 through lower outlet 256. Therefrigerant vapor 82 leaves separator 92 through upper outlet 257.

Weak solution 89 leaves the separator 92 at a pressure of 290 psia and atemperature of 255° F. and enters the second recuperator 95 throughsecond recuperator inner fluted-tube inlet 258. The second recuperator95 consists of two rows of fluted tube-in-tube helical windings locatedradially outwardly adjacent to first recuperator 86 and extendingvertically along the lower-upper and lower portions of the firstrecuperator 86. The second recuperator 95 is contained in the lowerupper and lower portions of the cylindrical outer-most generator-unitchamber 240 that is formed by the outer first recuperator housing 239,the generator unit housing 221, the generator unit ceiling 224 and thegenerator unit floor 230. As the weak solution 89 passes through thefluted inner tube 259 of the second recuperator 95, it transfersapproximately 50,000 btu/hr to the strong solution 83 in outer tube 260as the strong solution 83 is on its way to the first recuperator 86. Theweak solution leaves the second recuperator 95 through the innerfluted-tube outlet 261 and is then throttled substantiallyisenthalpically through valve 96 (FIG. 1) and arrives at connection 93at a temperature of 120° F. and a pressure of 70 psia.

High pressure vapor 82 from the upper outlet 244 of separator 91 entersthe second generator 81 through inner fluted-tube inlet at a temperatureof 415° F. and pressure of 1480 psia. While circulating through flutedinner tube 253, the vapor is condensed liberating approximately 18,000btu/hr to the intermediate solution 85 in outer tube 252. The condensedvapor 82 leaves the second generator 81 through inner fluted-tube outletat a temperature of about 260° F. Passage of the condensed vapor 82through expansion valve 110 reduces its temperature to 120° F. and itspressure to 290 psia. The expanded vapor 82 is joined with the vapor 82from the secondary separator 92 at connection 94.

After the vapor 82 is absorbed into the weak solution 89 in the absorber97 and the resulting strong solution 83 passes through the purge pot 99and pump 98, it enters the secondary recuperator 95 at a temperature of120° F. and a pressure of 1550 psia through outer tube inlet 264. Whilecirculating through the outer tube 260, the strong solution receives50,000 btu/hr from the weak solution 89 in the inner fluted tube 259 andan additional 1,000 btu/hr from the circulating flue gases 245. Onleaving the secondary recuperator 95 through outer tube outlet 265, thestrong solution 83 is at a temperature of 230° F. and a pressure of 1520psia.

From the secondary recuperator 95, the strong solution enters theprimary recuperator 86 through outer tube inlet 266. While circulatingthrough the outer tube 249, the strong solution 83 receives 69,000btu/hr from the intermediate solution 85 circulating in the fluted innertube 248 and an additional 1000 btu/hr from the circulating flue gases245. The strong solution 83 leaves the primary recuperator 86 throughouter tube outlet 267 at a temperature of 385° F. and a pressure of 1490psia.

Although the preferred embodiment is shown and described, otherarrangements may be suitable for different operating conditions. Forexample, the solutions within fluted tubes and that in the annulus maybe switched one for the other, especially in the low temperaturerecuperator 95 where it might be preferable not to have the higherpressure fluid in the annulus.

Absorber and Condenser Module

Referring to FIG. 9, an integrated absorber/condenser module providesfor the assembly of condenser 100 and absorber 97 components that areschematically shown in FIGS. 1-3. The absorber/condenser moduleintegrates in one interrelated assembly the various components of theapparatus that are associated with the use of the heat generated in thedriving heat source 84 for heating, cooling and defrosting.

It is to be noted that the primary (refrigerant) system, usingpreferably an ammonia/sodium thiocyanate refrigerant pair, is completelycontained in the outside heating and air conditioning unit 165 andoperates in continuous fashion without the switching of flows among thevarious components. The working subsystem, using preferably awater/glycol working fluid, transfers heat among the load (insidespace), ambient outside air, and outside heat exchanger depending onwhether the system is operating in a heating, cooling or defrostingmode.

Heat exchange between the refrigerant system and the hydronic workingfluid subsystem occurs in the absorber/condenser module 270 andspecifically in the absorber 97 and the condenser 100. Theabsorber/condenser module consists of an absorber 97, a purge pot 99, acondenser 100 and a third (tertiary) recuperator means 107. Thecondenser 100 and the tertiary recuperator 107 are preferably flutedtube-in-tube construction. The absorber 97 is of fluted tube-in-cylinderconstruction.

The purge pot 99 is centrally positioned substantially on a central axis271 of the annular components including the absorber 97, condenser 100and the third recuperator 107. Each component is constructed as asubstantially annular coil, or coils and/or plurality of verticallypositioned toruses or helical tubings. The absorber 97 and the thirdrecuperator 107 are juxtaposed to the condenser and are radially moredistant from the central axis 271.

The absorber/condenser module 270 is contained in cylindrical housing278 with a bottom 279 and top 280. Insulation 281 is provided betweenthe cylindrical housing 278 and the outer most components.

The absorber 97 consists of two windings of fluted tube enclosed in acylindrical space 276 formed by outer cylindrical absorber wall 284,outer condenser wall 285, absorber bottom 286 and absorber top 287. Theinner and outer windings are separated by cylindrical baffle 289. Baffle289 is attached to absorber top 287. Generally a winding may beconsidered as a plurality of coils juxtaposed one to the next in agenerally annular composite form, i.e., a cylindrical helix.

Weak solution and refrigerant mixture enter the outer winding of flutedtube 288 at the top of the absorber, flow generally downward and thengenerally upward in the inner winding, i.e. in directions generallyparallel to the axis of the absorption coils. Working fluid 275 enterscylindrical space 276 through inlet 103 and circulates generallydownward and through and among the spaces formed by the juxtaposedfluted-tube outer windings. The working fluid 275 passes beneath thelower edge of baffle 289 and then circulates generally up and throughand among the spaces formed by the juxtaposed fluted-tube innerwindings. The working fluid leaves absorber 97 through outlet 104.

Weak solution 89 meets the refrigerant 82 at connection 93 and entersthe absorber 97 through fluted inner-tube inlet 272 at a temperature ofabout 144° F. and a pressure of about 70 psia. The refrigerant 82 isabsorbed into the weak solution 89 with release of an absorption heat of52,000 btu/hr to the working fluid 275 circulating in cylindrical space276. Strong solution 83 leaves the absorber 97 through fluted inner-tubeoutlet 277 at a temperature of about 118° F. and a pressure of about 70psia.

After leaving absorber 97, strong solution 83 enters purge pot 99through inlet 282 and exits the purge pot through outlet 283. The purgepot is used to periodically remove non-condensable gases formed in thesystem through the vent line 310 and valve 311.

Preferably, the condenser 100 comprises a single winding of fluted tube293 i.e., a plurality of coils juxtaposed one to the next in generallyannular composite form, extending the vertical length of theabsorber/condenser unit 270 and enclosed in the cylindrical condenserspace 290 formed by inner cylindrical condenser wall 291, outercylindrical condenser wall 285, absorber/condenser top 287 and condenserbottom 292 i.e., tube-in-cylinder construction. Although less preferred,tube-in-tube construction my also be used. If tube-in-tube constructionis used, the working fluid preferably circulates in the outer tube.

Hydronic working fluid enters the condenser space 290 through inlet 102,circulates around and through the spaces formed by the juxtaposed coilsof fluted tube 293 in a direction generally parallel to center line 271(in cross flow to the flow of vapor 82 in tube 293) and leaves throughoutlet 113. Refrigerant vapor 82 enters the condenser 100 through inlet294 at a temperature of 120° F. and pressure of 290 psia. Vapor 82condenses in fluted tube 293 transferring a condensation heat of 27,000btu/hr to hydronic working fluid 275 circulating in condensercylindrical space 290. Condensed refrigerant vapor 82 leaves thecondenser through outlet 295 at a temperature of 100° F. and a pressureof 290 psia.

The third (tertiary) recuperator means 107 is a single flutedtube-in-tube winding juxtaposed radially outward from condenser 100.Condensed vapor 82 from condenser outlet 295 enters the tertiaryrecuperator 107 through fluted-tube inlet 296 and circulates throughinner fluted tube 297 where it transfers 610 btu/hr to vapor 82 in theouter tube 298. Condensed vapor 82 leaves tertiary recuperator 107through fluted-tube outlet 299 at a temperature of 90° F. and a pressureof 285 psia.

As shown in FIG. 4, evaporator 115 is a cylindrical unit with acylindrical outer housing 300, a cylindrical inner housing 301, a top303 and a bottom 304 forming cylindrical space 302. An annular windingof fluted tube 305 is contained in cylindrical space 302. Hydronicworking fluid 275 enters the evaporator 115 through inlet 118 andcirculates generally downward over, through and among the spaces formedfrom the juxtaposed windings of fluted tube 305. The hydronic fluid 275leaves the bottom of evaporator 115 through outlet 119.

After leaving the tertiary recuperator 107, condensed vapor 82 passesthrough expansion value 110 after which it enters evaporator 115 at apressure of 72 psia and a temperature of about 39° F. through evaporatorinlet 307. The condensed vapor 82 evaporates in fluted tube 305absorbing 36,000 btu/hr from the circulating hydronic working fluid inevaporator cylindrical space 302. The evaporated vapor 82 leavesevaporator 115 through outlet 306 at a temperature of about 53° F. and apressure of about 72 psia.

After leaving the evaporator, the refrigerant vapor 82 enters thetertiary recuperator 107 through outer tube inlet 308, circulatesthrough outer tube 298 receiving 610 btu/hr from the condensed vapor 82in inner fluted tube 297, and leaving by outer tube outlet 309 at atemperature of about 67° F. and a pressure of about 71 psia. Afterleaving the tertiary recuperator, vapor 82 enters accumulator 205.

Although the preferred embodiment is shown and described, otherarrangements may be suitable for different operating conditions. Forexample, the solutions within fluted tubes and that in the annulus maybe switched one for the other, especially in the low temperaturerecuperator 95 where it might be preferable not to have the higherpressure fluid in the annulus. The third recuperator 07 could also bemounted on the outside of the evaporator coil 115 in a fashion similarto the way it is shown as on the outside of the condenser 100. The purgepot 99 need not be inside the absorber/condenser. The chosen locationhowever does conserve space. An expansion tank to allow for expansionand contraction of the heat transfer fluid (ethylene glycol/water) couldsimilarly be placed inside the evaporator.

    ______________________________________                                        HYDRONIC WORKING FLUID TEMPERATURES                                                           INLET    OUTLET                                               ______________________________________                                        Condenser         105° F.                                                                           110° F.                                   Absorber          110        120                                              Evaporator         55         45                                              Outdoor Heat Exchanger                                                        Heating Mode       40         45                                              Cooling Mode      120        105                                              Indoor Heat Exchanger                                                         Heating Mode      120        105                                              Cooling Mode       45         55                                              ______________________________________                                    

Solution Pump and Energy Recovery Apparatus

In the operation of the absorption refrigeration system of thisinvention a mechanical energy input is necessary in addition to thethermal energy input. The necessary mechanical energy is primarilyrequired for operation of the solution pump which circulates thesolution pair through the system. In FIGS. 1, 2, and 3 the solution pump98 is shown conveying the strong solution from the absorber 97 to thefirst generator means 80 by way of the second and first recuperators 95and 86 respectively. In a system capacity of 36,000 BTU per hour, themechanical energy required to raise the solution pressure to about 1200PSIA is approximately 670 watts. Providing this mechanical energy usinga convention electric motor and pump would require consumption ofapproximately 1200 watts of electrical power which would reduce therefrigeration cycle efficiency (COP) by approximately 11%. The PriorPatent describes an energy recovery system for recovering energy fromthe isenthalpic throttling valves required for the system.

In this invention, an alternate energy recovery system has been furtherrefined as shown in FIGS. 10 and 11.

In FIG. 10, one embodiment of the improved energy recovery apparatusincludes rotary motor means 152 driving a positive displacement solutionpump means (which may be either rotary or reciprocating) 98 receivingstrong solution from the purge pot 99. The solution pump 98 raises thestrong solution to an and conveys the solution to a second higherpressure solution pump 157, where the pressure is raised to the highpressure requirements of the system before conveying the strong solutionthrough recuperators 95 and 86 to the first generator 80.

The second pump 157 may be located between low temperature recuperator95 and high temperature recuperator 86, (shown in phamton 370). In thatway both the pump 158 and motor(s) 157, 158, and 159 would all be atmore nearly equal temperatures. Also, both pipes of the low temperaturewould be at more nearly equal pressures--significantly lower than theprimary generator pressure.

The solution pump 157 is driven by energy recovery means 158 and,alternatively, also by additional energy recovery means 159.

Solution pump 98 is preferably an electric motor driven pump ofconventional design. Solution pump 157 may be either a rotary pump or areciprocating pump more suitable for high pressure service, being drivenby reciprocating expansion devices operating through the pressure letdown of the expansion means 87 and 105.

In the construction according to FIG. 10, the energy recovery motors arenot mechanically connected to the shaft of the motor 152 providing moreflexibility in the operation of the solution pump and energy recoveryarrangements than in the embodiment of the Prior Patent where theopposite direct connection was provided. Although the pressuresgenerated in the pumps 98 and 157 are additive to produce a sum pressureat the generator 80, each pump is operating independently under theinfluence of an independent motive system.

In FIG. 11, the motor 152' drives a solution pump 98'. The secondsolution pump 157' is driven in reciprocating motion by an energyrecovery device 158' connected to the pressure expansion valve 87. Inthis alternative embodiment the strong solution enters the pumps 98' and157' at the same suction pressure. However, on the discharge side, theoutlets from the pumps are combined at the same pressure. The flow tothe generator 80 is the sum of the two flows.

In either the embodiment of FIG. 10 or the embodiment of FIG. 11sufficient energy recovery is provided to contribute significantly tothe increase the COP to a range of about 0.8 in cooling mode.

Referring to FIG. 12, an energy recovery motor combining components 157and 158 is shown as energy recovery means 350. Unit 350 is fed bysolution pump 98. The output of solution pump 98 is divided and passesthrough check valve means 351 and 352 to opposite ends of thereciprocating piston pump 350 comprising a cylinder 353 centrallydivided into chambers 354 and 355 by opposite ends of a reciprocatingpiston 356. Piston 356 divides the chambers 354 and 355 into secondchambers 357 and 358 respectively. Chambers 354 and 355 are providedwith outlets through check valve means 360 and 361 respectively. Checkvalve means are connected together to provide a connection to the firstprimary generator means 80.

Solution 85 at high pressure is provided to the second chambers 357 and358 respectively through control valves 362 and 363 respectively.Solution leaves the chambers 357 and 358 through control valves 364 and365 to the secondary generator 81. The control valves 362, 363, 364 and365 operate to time the admission of high pressure solution to thechambers 357 and 358 and cause the piston 356 to reciprocate raising thesolution pressure to the higher level requirements at the primarygenerator 80. Energy recovery through reciprocating motion and devicesof this type are available from the Recovery Engineering Inc. ofMinneapolis, MN. The details of their construction and operation are nota part of this invention.

It is herein understood that although the present invention has beenspecifically disclosed with the preferred embodiments and examples,modifications and variations of the concepts herein disclosed may beresolved to by those skilled in the art. Such modification andvariations are considered to be within the scope of the invention andthe appended claims.

We claim:
 1. In an absorption refrigeration and/or heating system havingcomponents connected in series, including at least one generator, acondenser, an evaporator, and an absorber, wherein refrigerant isabsorbed and desorbed or expelled in an absorbent solution, and theapplication of heat and externally supplied mechanical energy iscombined and converted to pressure energy that is applied to, orremoved, from a solution of refrigerant and absorbent, and having meansto recover a portion of the pressure energy for addition to themechanical energy; the improvement comprising:(a) means to convert thepressure energy and/or phase change energy in the solution and/orrefrigerant to mechanical energy; (b) means to replace or supplement theexternally supplied mechanical energy in the system with the convertedmechanical energy; (c) said system including first positive displacementpump means for conveying the absorbent solution from the absorber to theat least one generator means, with said first pump means driven by amotive means that is activated by the externally supplied mechanicalenergy, and (d) a second pump means driven and controlled by the systempressure energy, as determined by the first positive displacement pumpmeans with each pumping means independently driven, and connected to theother, only by fluid connection means.
 2. The system of claim 1 whereinthe first pump means is an electric motor driven rotary pump.
 3. Thesystem and improvement of claim 1 wherein each pump means includes aninlet and an outlet; andthe outlet of the first pump means is in fluidconnection with the inlet of the second pump means.
 4. The system ofclaim 3 wherein the second pump means is a reciprocating pump.